1. Field of Invention
The present invention relates generally to improved methods and apparatuses for depositing films on partially fabricated integrated circuits (ICs). More specifically, the present invention relates to improved methods and apparatuses for accelerating the deposition of certain materials from precursors, such as organometallic compounds.
2. Description of the Prior Art
In integrated circuit fabrication, various materials are deposited on a substrate at various stages in the fabrication process. By way of example, metallization layers may be produced by processing (e.g., etching, chemical or physical vapor deposition, etc.) layers (e.g., metal layers) on a silicon wafer or substrate. By further way of example, dielectric layers may be formed between metallization layers to enable the formation of multi-level connections to devices, to produce field oxide regions used to isolate semiconductor active devices, to produce passivation layers used to protect entire IC chips during packaging, and to form masks used in subsequent etching processes.
There are many well-known techniques used for depositing materials, such as silicon dioxide (SiO2). Such techniques often include the use of a precursor (e.g., organometallic compounds) reactants, such as tetraethylorthosilicate xe2x80x9cTEOSxe2x80x9d Si(OC2H5)4. Such materials are introduced into a chemical vapor deposition (CVD) reactor chamber to break down and decompose to form films and by-products, such as SiO2 films and Si and organic by-products. TEOS is in a liquid state at room temperatures and must be heated in an external vaporizing apparatus, or otherwise converted to the gas phase, before being introduced into a CVD reactor chamber.
Although forming films from such precursors as TEOS is popular because generally good step coverage is provided and the required deposition temperatures are relatively low, precursors including TEOS are very expensive. Therefore, there is a need to utilize a high percentage of precursors in producing films (as opposed to being pumped out of the CVD reaction chamber as unused reactant).
At least three chemical vapor deposition processes are now commonly used in industry. These include plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), and atmospheric pressure chemical vapor deposition (APCVD). To formulate a SiO2 layer in any of these three chemical vapor deposition processes, oxygen and ozone are typically employed, especially if TEOS is the precursor. While the introduction of oxygen and ozone promotes TEOS decomposition, it has been found that TEOS decomposition reaction is still slow and a relatively high fraction of the TEOS introduced into a CVD chamber does not completely and fully react with the oxygen and ozone and is therefore wasted. Also, because TEOS decomposes at a slow rate, it has been found that the slow rate of decomposition causes certain structural defects (e.g., voids) resulting from the deposition of TEOS SiO2 films over gaps between vertical structures.
U.S. Pat. No. 5,710,079 to Sukharev attempts to solve these problems by providing a method and apparatus for facilitating the decomposition of organometallic compounds in chemical vapor deposition reactors in order to deposit films. In one embodiment for the method in U.S. Pat. No. 5,710,079, the method generally includes: (1) introducing an organometallic compound (e.g., TEOS) and ozone molecules to a chemical vapor deposition reactor; (2) directing ultraviolet radiation into the chemical vapor deposition reactor to increase the rate at which oxygen atoms are formed from the ozone molecules present in the chemical vapor deposition reactor; and (3) decomposing the organometallic compound to form a deposition layer (e.g., a silicon dioxide layer). The organometallic compound is taught as decomposing at an accelerated rate due in part to an increased concentration of hydroxyl radicals present in the chemical vapor deposition reactor. The hydroxyl radicals are produced from a reaction of oxygen atoms with moisture. The water vapor and/or hydrogen peroxide is introduced to the chemical vapor deposition reactor to ensure that a high concentration of hydroxyl radicals are present.
In one embodiment for the apparatus in U.S. Pat. No. 5,710,079, an apparatus for depositing a dielectric layer on a substrate is disclosed. The apparatus is preferably suited for decomposing organometallic compounds such as TEOS with the aid of hydroxyl radicals. The apparatus generally includes: (1) a chemical vapor deposition reactor having a support for a substrate, and at least one inlet port for receiving gases; (2) a source of ozone gas coupled to the at least one inlet port; (3) a source of the organometallic compound coupled to the at least one inlet port; and (4) a source of ultraviolet radiation oriented to direct ultraviolet radiation into the chemical vapor deposition reactor.
The deficiencies with the method and apparatus disclosed in U.S. Pat. No. 5,710,079 is that the CVD reactor chamber must be adapted to produce hydroxyl radicals in situ before the hydroxyl radicals commence to react with and decompose the organometallic compounds. This delays the formation of SiO2 films and causes inefficiencies. Also, the CVD reactor chamber must be built with a radiation transmission window such that ultraviolet light may be transmitted into the CVD reactor chamber in order to decompose ozone molecules to produce atomic oxygen which reacts with water to produce the hydroxyl radicals.
Therefore, what is needed and what has been invented is an improved method and apparatus for processing semiconductor substrates without the foregoing deficiencies and which includes depositing films on partially fabricated integrated circuits. What is further needed and what has been invented is an improved method and apparatus for forming a deposition layer, such as a SiO2 film, in a chemical vapor deposition reactor.
The present invention broadly provides a method for depositing a layer on a substrate in a chemical vapor deposition reaction zone comprising introducing a precursor into a chemical vapor deposition reaction zone containing a substrate, and introducing hydroxyl radicals into the chemical vapor deposition reaction zone for reacting with the precursor to form a deposition layer on the substrate. The precursor may be selected from the group consisting of silane, silicon, an organometallic compound, and a silicon-containing gas. The introduction of hydroxyl radicals into the chemical vapor deposition reaction zone comprises introducing hydroxyl radicals as a gas phase into the chemical vapor deposition zone. The gas phase preferably comprises at least about 10% by volume of the hydroxyl radicals, and the temperature of the gas phase preferably ranges from about 100xc2x0 C. to about 150xc2x0 C. An inert gas is typically employed as a carrier for the precursor. The inert gas may be any suitable inert gas, but is preferably selected from the group consisting of nitrogen, helium, argon, neon, krypton, xenon and radon, and mixtures thereof. The method for depositing a layer additionally comprises producing the hydroxyl radicals prior to the introducing hydroxyl radicals into the chemical vapor deposition reaction zone. Preferably hydroxyl radicals are introduced at a pressure ranging from about 100 Torr to about 200 Torr. Reacting the precursor with the hydroxyl radicals preferably decomposes the precursor to form the deposition layer.
The present invention further broadly provides a method for forming a deposition layer in a chemical vapor deposition reactor comprising the steps of (a) producing hydroxyl radicals; (b) admixing the produced hydroxyl radicals with a precursor to produce a hydroxyl radicals-precursor mixture; and (c) introducing the hydroxyl radicals-precursor mixture of step (b) into the chemical vapor deposition reactor to form a deposition layer. The producing of hydroxyl radicals in step (a) preferably comprises introducing a water-containing agent (e.g., water) and ozone into a hydroxyl radical-producing reactor; and directing ultraviolet radiation into the hydroxyl radical-producing reactor to cause oxygen atoms to form from the ozone and react with the water-containing agent to produce hydroxyl radicals. The method additional comprises removing, prior to the admixing of step (b), hydroxyl radicals from the hydroxyl radical-producing reactor. The admixing of hydroxyl radicals with the precursor causes the hydroxyl radicals to react with the precursor. Preferably, the hydroxyl radicals and the precursor are reacting as the hydroxyl radicals-precursor mixture is being introduced into the chemical vapor deposition reactor.
The present invention also broadly provides a chemical vapor deposition reactor for forming deposition films comprising a chemical vapor deposition reactor chamber; a source of hydroxyl ion gas coupled to the chemical vapor deposition reactor chamber and including hydroxyl ion gas flowing or introducing into the chemical vapor deposition reactor chamber; and a pedestal disposed in the reactor chamber for supporting substrates in the reactor chamber. The chemical vapor deposition reactor also comprises a processing power source; a processing gas-introducing assembly engaged to the reactor chamber for introducing a processing gas into said reactor chamber; and a processing power-transmitting member disposed in proximity to the reactor chamber and connected to the processing power source for transmitting power into the reactor interior for forming deposition films. The source of hydroxyl ion gas comprises a hydroxyl-ion producing reactor having at least one inlet port; a source of water coupled to the at least one inlet port; a source of ozone gas also coupled to the at least one inlet port; and a source of ultraviolet radiation oriented to direct ultraviolet radiation into the hydroxyl-ion producing reactor.
The present invention further also broadly provides a chamber assembly for decomposing a precursor with hydroxyl radicals comprising a process chamber having a support for a substrate and at least one port for receiving at least one gas; a source of precursor gas coupled to the at least one port for flowing precursor gas into the processing chamber; a source of hydroxyl radical gas coupled to the at least one port for flowing or introducing hydroxyl radical gas into the processing chamber to cause the precursor gas to decompose. Further provided in accordance with the present invention is a reactor for processing substrates comprising a reactor chamber; a hydroxyl-ion producing assembly coupled to the reactor chamber for producing hydroxyl ions and introducing the hydroxyl ions into the reactor chamber; and a pedestal disposed in the reactor chamber for supporting substrates in the reactor chamber. The reactor also comprises a processing power source; a processing gas-introducing assembly engaged to the reactor chamber for introducing a processing gas into the reactor chamber; and a processing power-transmitting member disposed in proximity to the reactor chamber and connected to the processing power source for transmitting power into the reactor interior.